The present invention relates to a continuously variable transmission which incorporates a continuously variable ratio device (“variator”) and is able to produce a range of output gearing ratios wider than the range provided by the variator using a planetary gear mechanism and employing power recirculation. More specifically, it relates to a continuously variable transmission in which the input shaft and the output shaft are coaxially disposed.
A continuously variable transmission has already been proposed which uses a toroidal type of variator and in which various parts are disposed coaxially (see WO 03/100295 A1). As shown in FIG. 6 (a), the said continuously variable transmission 1 incorporates: a toroidal race, rolling traction variator 5 comprising an input disc 2, an output disc 3 and rollers 4 which are disposed between these two discs and which are able to alter their position of radial contact with the two discs; a planetary gear mechanism 6 having a carrier C1 supporting three pinions P1, P2 and P3 mutually spaced along the axial direction; a reversing gear mechanism 7 having a cattier C2 supporting two pinions P4 and P5 which are spaced along the axial direction; and a high/low regime change mechanism 10 comprising a low brake L able to stop a sun gear S4 on the output side of the reversing gear mechanism, and a high clutch H interposed between a second sun gear (high-mode output gear) S2 of the planetary gear and an output shaft 13. These members are arranged coaxially between the input shaft 12 and the output shaft 13.
Thus, in a low regime, in which the low brake L is engaged and the high clutch H is disengaged, the known continuously variable transmission 1 uses the planetary gear mechanism 6 to combine the rotations of the carrier C1 (directly inputting the rotation of the input shaft 12) and the sun gear S1 on the input side, which has been reversed and geared via the directly inputting carrier CT and variator 5, and outputs the result to a low-mode output gear (third sun gear) S3. The planetary gear mechanism 6 also reverses the rotation of the said output gear S3 and outputs the result to the output shaft 13.
It will be appreciated that, as shown in FIG. 6 (b), the low/high regime change mechanism 10 may also be configured using a low clutch L interposed between a carrier C2 and the output shaft 13, and a high clutch H similar to the one above interposed between the second sun gear S2 of the planetary gear and the output shaft 13.
The known continuously variable transmission has large axial length since the planetary gear mechanism 6 comprises three pinions P1, P2 and P3 which are separated along the axial direction, and the reversing gear mechanism 7 also comprises two pinions P4 and P5 which are separated along the axial direction.